Some spatial light modulator (SLM) based projection systems can generate a displayed image having a higher resolution (greater pixel density) than the SLM used to generate the displayed image. For example, an SLM-based projector may include a moving glass plate interposed in the light path after the light has been modulated by the SLM. An actuator moves the plate so that, in one position, the output of the projector shifts by one-half pixel in both the x and y directions. This shift places the center of the shifted pixels at the intersection of four of the unshifted pixels. The output of the SLM alternates between the pixel information for unshifted and shifted pixels rapidly enough that the eye sees the combination of the unshifted and shifted pixels as an image having double the resolution of the SLM. This technique may be extended to further increase the resolution of the displayed image by moving the glass plate to more sub-pixel positions (e.g., four positions).